Conventionally, there has been known a lighting device configured to supply direct current (DC) power to a light source. The lighting device includes a DC power supply configured to convert an alternating current (AC) voltage into a DC voltage in response to an AC power. The light source includes a solid-state light emitting element(s) such as a light emitting diode(s) (LED).
For example, a lighting device disclosed in Document 1 (JP2014-130768A) can operate any of multiple kinds of light sources having different forward voltages. Specifically, the lighting device of Document 1 is configured to detect a forward voltage, which is defined as a voltage drop across the light source, and compare the detected forward voltage with two or more threshold values, thereby determining which kind of light source is connected to the lighting device.
Incidentally, when supply of power from an external power supply to a lighting device is stopped (when the power supply is off), the light source connected to the lighting device is turned off. However, the conventional lighting device, which can operate any of the multiple kinds of light sources having different forward voltages, has a difficulty in detecting whether a light source connected thereto is turned off (is in a turned-off state) or not.
When the lighting device cannot detect the turned-off state of the light source (cannot detect that the light source is turned off) at the time the power supply is off, a dimming control by the lighting device may be performed incorrectly after the lighting source is turned on again.
It is therefore desired a lighting device and a luminaire, which can operate any of multiple kinds of light sources having different forward voltages, and can certainly determine a turned-off state of the light source connected thereto as the load when a power supply is off.